Did you check your settings how it was set to open a new tab?

Please tell me how to correct this situation.

See the Tabs section on Options/Preferences -> General

Does that only happen with that specific page?

Are you using a bookmark or do you click a link on the web page.

See also:

• http://kb.mozillazine.org/browser.link.open_newwindow
• 1: current tab; 2:new window; 3:new tab;

For links opened via JavaScript you can look at this pref:

• http://kb.mozillazine.org/browser.link.open_newwindow.restriction

You can open the about:config page via the location/address bar. You can accept the warning and click "I accept the risk!" to continue.

• http://kb.mozillazine.org/about:config

tricia2 said

1.when I go to a site it always opens in a new window instead of a tab .2. also when I search and the page shows choices I would like each site to go to new tab so I don't have to hit back butt on to get back to the search page

Could it be that you accidentally press the Shift key and + sign, instead of the Ctrl key and + sign  ?

tricia2 said

2. also when I search and the page shows choices I would like each site to go to new tab so I don't have to hit back butt on to get back to the search page

Each search site has this in a different place, but on Google, for example:

https://www.google.com/preferences

It's the "Where results open" section.

You'll see that mentions opening in a new window because sites can't specify tab, just window. Firefox will divert the new window to a new tab instead if that Firefox setting is enabled.

Success?